Heat exchanger

ABSTRACT

A heat exchanger for an appliance having a burner includes at least one tubular heat exchanger section extending from an inlet end aligned with the burner and an outlet end. The inlet end includes a first portion having a first inner diameter and a second portion having a second inner diameter greater than the first diameter.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Appln. No.62/472,842, filed Mar. 17, 2017, the entirety of which is incorporatedherein by reference.

TECHNICAL FIELD

The present invention relates generally to burner systems and, morespecifically, relates to a heat exchanger for a burner.

BACKGROUND

Requirements for NO_(x) emissions continue to become more stringent.California's South Coast Air Quality Management District is the worldleader in NOx regulations. Recently enacted legislation for forced airfurnaces have caused a shift in the type of combustion required forthese products. Inshot burners, which have been the industry standardfor many years are not capable of meeting the new NO_(x) requirements.Inshots are relatively low primary aeration burners, which typicallyfired into a tubular type heat exchanger. Secondary air is introducedaround the perimeter of the centrally located flame. The secondary airgradually enters the flame to complete the combustion as it makes itsway down the length of the tube. The secondary air also shields the tubeinlet from exposure to the flame as it enters the tube.

The relatively low primary air flame also has a lower flame temperaturethan a more highly aerated premixed flame. Since most furnacemanufacturers make high volumes of furnaces for sale throughout thecountry, it is not practical or cost effective to make a completely newfurnace model for the California market. The desire of thesemanufactures is to use as much of the existing furnace as possible, withonly the burner changing to meet the requirements. The best option formeeting the requirements is to switch to a fully premixed burner system.This system, however, can cause overheating of the vestibule panel andheat exchanger tubes.

SUMMARY

In one example, a heat exchanger for an appliance having a burnerincludes at least one tubular heat exchanger section extending from aninlet end aligned with the burner and an outlet end. The inlet endincludes a first portion having a first inner diameter and a secondportion having a second inner diameter greater than the first diameter.

In another example, a furnace includes a burner including a distributorhaving at least one curved second portion for providing a flame. Avestibule panel connected to the burner includes an opening aligned witheach second portion downstream of the burner. A heat exchanger has atleast one tubular heat exchanger section extending from an inlet endaligned with each second portion of the burner and an outlet end. Theinlet end includes a first portion having a first inner diameter and asecond portion having a second inner diameter greater than the firstdiameter.

In yet another example, a heat exchanger for an appliance having aburner includes a plurality of heat exchanger sections each extendingfrom an inlet end aligned with the burner and an outlet end. The inletand outlet ends are positioned on the same side of the heat exchangersection. Each inlet end includes a first portion having a first innerdiameter and a second portion having a second inner diameter greaterthan the first diameter A ceramic insulation sleeve is positioned withinthe second portion of each heat exchanger section and has an innerdiameter substantially equal to the first diameter of the inlet end. Theinsulation sleeve helps to protect the inlet end from thermal damage.

Other objects and advantages and a fuller understanding of the inventionwill be had from the following detailed description and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic illustration of an appliance including a heatexchanger in accordance with the present invention.

FIG. 2A is an assembly view of components including the heat exchangerin the appliance of FIG. 1.

FIG. 2B is an exploded view of alternative components of the appliance.

FIG. 3 is a side view of a heat exchanger section of the heat exchangerin FIG. 2A.

FIG. 4 is a section view of FIG. 3 taken along line 4-4.

FIG. 5 is a front view of a vestibule panel of the appliance of FIG. 1A.

FIG. 6 is a section view of FIG. 5 taken along line 6-6.

FIG. 7A is a front view of an insulation sleeve for the heat exchangersection of FIG. 3.

FIG. 7B is an enlarged view of a portion of the heat exchanger sectionof FIG. 3 including the insulation sleeve of FIG. 7A.

FIG. 8 is a schematic illustration of operation of the heat exchanger ina first example.

FIG. 9 is a schematic illustration of operation of the heat exchanger ina second example.

DETAILED DESCRIPTION

The present invention relates generally to burner systems and, morespecifically, relates to a heat exchanger for a burner. Referring toFIG. 1, the heat exchanger is provided in an appliance, such as afurnace 10. In one example, the furnace 10 includes a heat exchanger 20,vestibule panel 40, burner 50, gasket 60, and an inducer blower 68 (FIG.2A). Alternatively, the furnace 10 can include the heat exchanger 20,vestibule panel 40 a, burner 50, gasket 60, and a secondary heatexchanger 80 (see FIG. 2B). The burner 50 can be positioned nearer thebottom of the vestibule panel 40 (FIG. 2A) or nearer the top of thevestibule panel 40 a (FIG. 2B) depending on the configuration of theappliance 10. The remainder of the description is directed to theappliance 10 component configuration of FIG. 2A unless otherwise noted.

As shown in FIGS. 3-4, the heat exchanger 20 includes at least one heatexchanger section 22. Although five sections 22 are shown it will beappreciated that more or fewer sections—including a single section—canbe provided. The sections 22 are hollow and substantially identical toone another.

Each heat exchanger section 22 is formed as a serpentine tube extendingalong a centerline 23 from a first or inlet end 24 to a second or outletend 26. The inlet end 24 terminates at an opening 25 and the outlet end26 terminates at an opening 27. As shown, the ends 24, 26 and thereforethe openings 25, 27 are positioned on the same [left] side of the heatexchanger section 22. Alternatively, the ends 25, 26 and openings 25, 27could be positioned on opposite sides of the heat exchange section 22(FIG. 2B). In any case, a passage 30 extends the entire length of thesection 22 from the opening 25 to the opening 27.

The inlet end 24 of each heat exchanger section 22 includes a wall 70defining a first portion 74 and a second portion 76 upstream of thefirst portion. The first portion 74 has a first inner diameter Φ₁ andthe second portion 76 has a second inner diameter Φ₂ greater than thefirst inner diameter. A tapered or angled neck 78 connects the first andsecond portions 74, 76 together. The heat exchanger section 22 can havesubstantially the same first inner diameter Φ₁ from the neck 78 to theopening 27 in the outlet end 26. Alternatively, the first inner diameterΦ₁ can taper down in a direction extending towards the opening 27 in theoutlet end 26 (not shown).

Referring to FIGS. 5-6, the vestibule panel 40 can be planar andincludes opposing sides 42, 44. A layer of thermal insulation (notshown) can line at least a portion of the side 44. First openings 43 andsecond openings 45 extend entirely through the vestibule panel 40between the sides 42, 44. The number of first openings 43 and secondopenings 45 each corresponds with the number of heat exchanger sections22. The first openings 43 are positioned nearer the bottom of thevestibule panel 40. The second openings 45 are positioned nearer the topof the vestibule panel 40. The first openings 43 could, however, belocated nearer the top of the vestibule panel 40 a (see FIG. 2B).

The sections 22 are connected to the vestibule panel 40 via a swaged orwelded connection 46 (FIG. 2A). The inlet ends 24 of the sections 22 arepositioned in the openings 43 in the vestibule panel 40. This aligns theopenings 25 in the inlet ends 24 with the openings 43 in the vestibulepanel 40. The outlet ends 26 are positioned in the openings 45 in thevestibule panel 40 and connected thereto by swaging or welding at 46.This aligns the openings 27 in the outlet ends 26 with the openings 45in the vestibule panel 40. The fluid passage 30 of each section 22 istherefore fluidly connected with a corresponding pair of openings 43, 45in the vestibule panel 40.

As shown in FIGS. 2A-2B, the burner 50 is positioned upstream of thevestibule panel 40 and the sections 22, i.e., secured to the side 42 ofthe vestibule panel. The burner 50 can constitute a non-premixed burneror a pre-mixed burner. The premixed burner can be partially or fullypremixed. In one example, the burner 50 is a fully premixed, low NO_(x)burner. The burner 50 includes a housing 52 defining a combustionchamber 54 therein. A distributor 56 is secured to the housing 52 toclose the combustion chamber 54.

The distributor 56 is formed from a thin, durable, and heat-resistantmaterial such as metal, a metal screen or expanded metal. Thedistributor 56 includes a planar first portion 57 and at least onedimple or second portion 58 formed or provided on the first portion. Inone example, each second portion 58 is curved or dimple-shaped, e.g.,rounded, hemispherical, concave or convex. Every second portion 58 mayhave the same configuration or different configurations from oneanother. A concave second portion 58 provides a narrow, long orelongated flame while a convex second portion will provide a wider, moredispersed flame.

The number, size, and spacing of the second portions 58 coincides withthe number, size, and spacing of the downstream first openings 43 andheat exchanger sections 22 present. In particular, each second portion58 is aligned with the inlet end 24 of an associated heat exchangersection 22 such that the end of each section is in fluid communicationwith each second portion. Each second portion 58 can be configured toprovide a desired flame characteristic or profile from the burner 50 tothe respective heat exchanger section 22.

The gasket 60 is positioned between the distributor 56—more specificallythe entire burner 50—and the side 42 of the vestibule panel 40. Thegasket 60 includes a plurality of openings 62. Each opening 62 isaligned with one of the second portions 58 on the distributor 56 and oneof the first openings 43 in the vestibule panel 40. The openings 62 arealso each aligned with one of the inlet ends 24—more specifically theopenings 25 therein—of the sections 22 on the opposite side 44 of thevestibule panel 40.

Referring to FIGS. 7A-7B, an optional insulation sleeve 90 can beinserted into the first end 24 of each heat exchanger section 22. Theinsulation sleeve 90 is tubular and includes a passage 91 extendingbetween a pair of openings 92, 94. The insulation sleeve 90 has an innerdiameter Φ₃ substantially equal to the first diameter Φ₁ of the firstportion 74 and a radial thickness “t”. The insulation sleeve 90 can bemade from any thermally insulating material, such as a ceramic orglass/silica fiber.

The insulation sleeve 90 is inserted into the second portion 76 of theheat exchanger section 22 until one end adjacent the opening 94 abuts oris in close proximity with the neck 78. The other end of the insulationsleeve 90 adjacent the opening 92 is aligned with the opening 43 in thevestibule panel 40. The insulation sleeve 90 is held in place byfriction with the second portion 76, the neck 78, and/or the gasket 60.As a result, the openings 92, 94 of each insulation sleeve 90 arealigned with an opening 43 in the vestibule panel 40, an opening 62 inthe gasket 60, and one of the second portions 58 of the burner 50 (seeFIG. 2B).

The third diameter Φ₃ and thickness t of the insulation sleeve 90 areconfigured such that when the insulation sleeve is provided within thesecond section 76, the sleeve radially abuts the wall 70 and the sleevepassage 91 is longitudinally aligned with the first portion 74. As aresult, there is no radial air gap between the insulation sleeve 90 andthe wall 70. The radially innermost structure within the section22—either the insulation sleeve 90 material or the wall 70 inner surfaceof the first section 74—has a substantially constant diameter.

As shown in FIG. 8, in operation flames F emanating from each secondportion 58 extend through the associated opening 62 of the gasket 60,the opening 43 in the vestibule panel 40, and into the opening 25 at theinlet end 24 of the associated heat exchange section 22. The flames Fare tailored such that the tip of each flame terminates at or adjacentto the opening 25 in the inlet end 24 of each section 22, i.e., theflames may barely extend into the interior of each tube and thereforebarely extend into the insulation sleeve 90. Alternatively, it will beappreciated that the insulation sleeve 90 described herein can beomitted from one or more of the inlet ends 24 (see FIG. 9) and, thus,the flame F would barely extend into the second portion 76 of the inletend 24.

When the burner 50 is a premixed burner, the very short flame F andrapid release of heat can cause the vestibule panel 40 and/or inlet ends24 of the heat exchanger sections 22 to overheat. The sleeve 90 of thepresent invention helps alleviate these overheating concerns byproviding insulation within the inlet ends 24 of the heat exchangersections 22.

In particular, the insulation sleeve 90 described herein helps protectthe material forming the inlet end 24 from thermal damage due to theincreased heat provided by the pre-mix/low NO_(x) burner 50. That said,the length of the second portion 76 and the length of the insulationsleeve 90 can be tailored to provide a desired degree of temperaturereduction/protection within the inlet end 24. Where the insulationsleeve is omitted in FIG. 9, the expanded second portion 76 helpsprotect the smaller diameter first portion 74 by providing enough spacenear/around the flame such that the wall 70 is not damaged or heatedbeyond its rating/allowable limit.

Furthermore, an abrupt change in the inner diameter along the inlet end24 could cause overheating within the inlet end as well as turbulencefor combustion products flowing therethrough. By providing the inlet end24 of each section 22 with a substantially constant inner diameter Φ₁the abrupt diameter change is avoided and no increase in pressure occursat the transition between the insulation sleeve 90 and the neck 78.

What have been described above are examples of the present invention. Itis, of course, not possible to describe every conceivable combination ofcomponents or methodologies for purposes of describing the presentinvention, but one of ordinary skill in the art will recognize that manyfurther combinations and permutations of the present invention arepossible. Accordingly, the present invention is intended to embrace allsuch alterations, modifications and variations that fall within thespirit and scope of the appended claims.

What is claimed is:
 1. A heat exchanger for an appliance having aburner, comprising: at least one tubular heat exchanger sectionextending from an inlet end aligned with the burner and an outlet end,wherein the inlet end includes a first portion having a first innerdiameter and a second portion having a second inner diameter greaterthan the first diameter.
 2. The heat exchanger recited in claim 1,wherein the second portion of the inlet end is positioned upstream ofthe first portion.
 3. The heat exchanger recited in claim 2, wherein thesecond portion defines an opening at the axial extent of the inlet end.4. The heat exchanger recited in claim 1 further comprising aninsulation sleeve positioned within the second portion and having aninner diameter substantially equal to the first diameter of the inletend, the insulation sleeve helping to protect the inlet end from thermaldamage.
 5. The heat exchanger recited in claim 4, wherein the at leastone heat exchanger section comprises a plurality of heat exchangersections, each including the second portion and an insulation sleeveprovided therein.
 6. The heat exchanger recited in claim 4, wherein theinsulation sleeve is tubular and includes a passage extending betweenfirst and second openings aligned with the first portion of the heatexchanger section.
 7. The heat exchanger recited in claim 2, wherein theinsulation sleeve is ceramic.
 8. The heat exchanger recited in claim 1,wherein the inlet end has a swaged connection with a vestibule panel ofthe appliance.
 9. The heat exchanger recited in claim 1, wherein theinlet end and outlet end are positioned on the same side of the heatexchanger section.
 10. The heat exchanger recited in claim 1, whereinthe inlet end and outlet end are positioned on opposite sides of theheat exchanger section.
 11. The heat exchanger recited in claim 1,wherein the inlet end receives a flame from a low NO_(x) burner.
 12. Afurnace comprising: a burner including a distributor having at least onecurved second portion for providing a flame; a vestibule panel connectedto the burner and including an opening aligned with each second portiondownstream of the burner; and a heat exchanger comprising at least onetubular heat exchanger section extending from an inlet end aligned witheach second portion of the burner and an outlet end, wherein the inletend includes a first portion having a first inner diameter and a secondportion having a second inner diameter greater than the first diameter.13. The furnace recited in claim 12 further comprising an insulationsleeve positioned within the second portion of the heat exchangersection and having an inner diameter substantially equal to the firstdiameter of the inlet end, the insulation sleeve helping to protect theinlet end from thermal damage.
 14. The furnace recited in claim 12,wherein the second portion of the inlet end is positioned upstream ofthe first portion.
 15. The furnace recited in claim 12, wherein thesecond portion defines an opening at the axial extent of the inlet end.16. The furnace recited in claim 12 further comprising an insulationsleeve positioned within the second portion and having an inner diametersubstantially equal to the first diameter of the inlet end, theinsulation sleeve helping to protect the inlet end from thermal damage.17. The furnace recited in claim 16, wherein the at least one heatexchanger section comprises a plurality of heat exchanger sections, eachincluding the second portion and an insulation sleeve provided therein.18. The furnace recited in claim 16, wherein the insulation sleeve istubular and includes a passage extending between first and secondopenings aligned with the first portion of the heat exchanger section.19. The furnace recited in claim 16, wherein the insulation sleeve isceramic.
 20. The furnace recited in claim 16, wherein the inlet end hasa swaged connection with each opening in the vestibule panel.
 21. Thefurnace recited in claim 12, wherein the inlet end and outlet end arepositioned on the same side of the heat exchanger section.
 22. Thefurnace recited in claim 12, wherein the inlet end and outlet end arepositioned on opposite sides of the heat exchanger section.
 23. Thefurnace recited in claim 12, wherein the burner is a low NO_(x) burner.24. A heat exchanger for an appliance having a burner, comprising: aplurality of heat exchanger sections each extending from an inlet endaligned with the burner and an outlet end, the inlet and outlet endsbeing positioned on the same side of the heat exchanger section, whereineach inlet end includes a first portion having a first inner diameterand a second portion having a second inner diameter greater than thefirst diameter; and a ceramic insulation sleeve positioned within thesecond portion of each heat exchanger section and having an innerdiameter substantially equal to the first diameter of the inlet end, theinsulation sleeve helping to protect the inlet end from thermal damage.